Field of the Invention
The present invention relates to a manufacturing method of a power-module substrate for a semiconductor device controlling a large electric current and high voltage.
Priority is claimed on Japanese Patent Application No. 2012-275157, filed Dec. 17, 2012, the content of which is incorporated herein by reference.
Description of the Related Art
Conventionally, it is known that a power-module substrate has a structure in which a metal plate is laminated to form a circuit layer on one surface of a ceramic substrate, and a metal plate is laminated to form a heat-radiation layer on the other surface of the ceramic substrate. Electronic components such as a semiconductor chip and the like is soldered on the circuit layer; and a heat sink is bonded on the heat-radiation layer.
In power-module substrates of this kind, there is a case in which the metal plate forming the circuit layer is made of copper having an excellent electrical characteristic, and the metal plate forming the heat-radiation layer is made of aluminum in order to buffer thermal stress with respect to the ceramic substrate.
For example, Patent Document 1 discloses a circuit substrate in which a copper plate is bonded on one surface of a ceramic substrate and an aluminum plate is bonded on the other surface. In this case, the ceramic substrate and the copper plate are bonded to each other by brazing material of reactive metal; and the ceramic substrate and the aluminum plate are bonded to each other by Al—Si based brazing material. In a case in which Ag—Cu—Ti based reactive-metal brazing material is used, bonding temperature is 800 to 930° C. Bonding temperature by the Al—Si based brazing material is 500 to 650° C.